// Copyright (c) 2012 The Chromium Authors. All rights reserved.
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.

// This file contains the command parser class.

#ifndef GPU_COMMAND_BUFFER_SERVICE_CMD_PARSER_H_
#define GPU_COMMAND_BUFFER_SERVICE_CMD_PARSER_H_

#include "gpu/command_buffer/common/cmd_buffer_common.h"
#include "gpu/command_buffer/common/constants.h"
#include "gpu/gpu_export.h"

namespace gpu {

class AsyncAPIInterface;

// Command parser class. This class parses commands from a shared memory
// buffer, to implement some asynchronous RPC mechanism.
class GPU_EXPORT CommandParser {
public:
    static const int kParseCommandsSlice = 20;

    explicit CommandParser(AsyncAPIInterface* handler);

    // Sets the buffer to read commands from.
    void SetBuffer(
        void* shm_address,
        size_t shm_size,
        ptrdiff_t offset,
        size_t size);

    // Gets the "get" pointer. The get pointer is an index into the command
    // buffer considered as an array of CommandBufferEntry.
    CommandBufferOffset get() const { return get_; }

    // Sets the "get" pointer. The get pointer is an index into the command buffer
    // considered as an array of CommandBufferEntry.
    bool set_get(CommandBufferOffset get)
    {
        if (get >= 0 && get < entry_count_) {
            get_ = get;
            return true;
        }
        return false;
    }

    // Sets the "put" pointer. The put pointer is an index into the command
    // buffer considered as an array of CommandBufferEntry.
    void set_put(CommandBufferOffset put) { put_ = put; }

    // Gets the "put" pointer. The put pointer is an index into the command
    // buffer considered as an array of CommandBufferEntry.
    CommandBufferOffset put() const { return put_; }

    // Checks whether there are commands to process.
    bool IsEmpty() const { return put_ == get_; }

    // Processes one command, updating the get pointer. This will return an error
    // if there are no commands in the buffer.
    error::Error ProcessCommands(int num_commands);

    // Processes all commands until get == put.
    error::Error ProcessAllCommands();

private:
    CommandBufferOffset get_;
    CommandBufferOffset put_;
    CommandBufferEntry* buffer_;
    int32 entry_count_;
    AsyncAPIInterface* handler_;
};

// This class defines the interface for an asynchronous API handler, that
// is responsible for de-multiplexing commands and their arguments.
class GPU_EXPORT AsyncAPIInterface {
public:
    AsyncAPIInterface() { }
    virtual ~AsyncAPIInterface() { }

    // Executes a single command.
    // Parameters:
    //    command: the command index.
    //    arg_count: the number of CommandBufferEntry arguments.
    //    cmd_data: the command data.
    // Returns:
    //   error::kNoError if no error was found, one of
    //   error::Error otherwise.
    virtual error::Error DoCommand(
        unsigned int command,
        unsigned int arg_count,
        const void* cmd_data)
        = 0;

    // Executes multiple commands.
    // Parameters:
    //    num_commands: maximum number of commands to execute from buffer.
    //    buffer: pointer to first command entry to process.
    //    num_entries: number of sequential command buffer entries in buffer.
    //    entries_processed: if not 0, is set to the number of entries processed.
    virtual error::Error DoCommands(unsigned int num_commands,
        const void* buffer,
        int num_entries,
        int* entries_processed);

    // Returns a name for a command. Useful for logging / debuging.
    virtual const char* GetCommandName(unsigned int command_id) const = 0;
};

} // namespace gpu

#endif // GPU_COMMAND_BUFFER_SERVICE_CMD_PARSER_H_
